1. Field of the Invention
This invention relates generally to a system and method for recharging an electric storage battery using a charger coupled to a power supply circuit that may have a current-drawing appliance in the circuit.
2. Description of the Prior Art
A hybrid vehicle is a vehicle that uses two distinct power sources, such as an on-board rechargeable energy storage system and a fueled power source for vehicle propulsion. The term hybrid vehicle most commonly refers to hybrid-electric vehicle (HEV), which use internal combustion engines and electric batteries to power electric motors. Generally, kinetic energy of the vehicle is recovered during braking, converted to electric energy and stored in one of the batteries.
A plug-in hybrid electric vehicle (PHEV) is a hybrid, which has additional battery capacity and the ability to be recharged from an external electrical outlet supplied by a public utility power grid. The vehicle can be used for short trips of moderate speed without needing the internal combustion engine (ICE) component of the vehicle's power train, thereby saving fuel costs. In this mode of operation, the vehicle operates as a pure battery electric vehicle, but the long range and additional power of the ICE power train is available when needed. PHEVs are commonly called “grid-connected hybrids.”
PHEVs require the user of its battery charging system to plug a vehicle charger into an AC outlet. In many cases this outlet is one of several on the same circuit breaker. To charge the vehicle's battery it is desirable to draw the maximum continuous current, at which the circuit is rated. However if other appliances are also connected to the same circuit, the maximum amount of available charger current is reduced. In this case, the charger could easily exceed the circuit maximum current draw and open a circuit breaker or fuse in the circuit resulting in no charge to the battery.
There is a need in the industry to detect the presence of other loads on the same circuit in addition to the charger so that the charger could reduce its load on the circuit, thereby reducing or eliminating the probability that the circuit breaker will open the circuit due to charging the battery.